one knot difference?

Here’s a good topic – see if you can help.

We are finding the boat a full knot quicker on port than we are on starboard and for sure we have a fairer shape to the main on port with quite the bubble in the luff of the main on Port.

We tuned the mast using the North Guide and a Loos Gauge when we stepped the mast and I plan to go back to review it now in pursuit of a solution. Looking at the sail it occurred to me that a hook in the middle of the mast might cause this but sighting up the mast one is not obvious.

Where would you Folks look first for a solution? We are comfortably hitting our polar target on the weaker tack though perhaps not able to point as high as we might like, especially at higher wind speeds where we are managing the traveler to keep the heel in range and the rudder engaged.  Jump in!